With the rapid technology development nowadays, optoelectronic elements have become widely used in our daily lives. In recent years, research to the optoelectronic elements has focused on enhancing the efficiency of the optoelectronic elements. Typically, optoelectronic elements may include photodetectors and solar cells. Implementations of the photodetectors include visible light detectors, which are photodetectors that can be utilized in the digital cameras, and optical pickup heads of digital optical drives. Generally, the surface of a visible light detector may be applied with surface plasma effect to strengthen the incident light such that efficiency may be enhanced. For example, Taiwan Patent No. 1335084, entitled “FULL COLOR MULTI-PIXEL PHOTODETECTOR DEVICE” utilizes the surface plasma effect, which responds only in certain wavebands and bandwidths, to enhance the detectability of photodetectors by detecting incident light in the certain wavebands. Moreover, a photodetector may include an infrared detector, which is applicable in military and general purpose uses. For example, a quantum well infrared detector does not absorb normal incident light, and requires additional optical guidance mechanism to transform a normal incident light in the TE mode, which is perpendicular to the horizontal surface, to the incident light in the TM mode, which is parallel to the horizontal surface. Typically, the application also utilizes surface plasma effect to enhance the detectability. Lastly, the solar cell is also an important technology due to the fact that sunlight is an unlimited natural source available in the foreseeable future, and that electricity obtained by transforming the optical energy of the sunlight may be utilized in a variety of power devices. For example, Taiwan Patent Publication No. 201230376, entitled “THIN-FILM SOLAR CELL OPTICAL CONFINEMENT AND INTEGRATION METHOD AND STRUCTURE THEREOF” utilizes the high scattering efficiency and strong near field optical effect of the surface plasma nanostructure to increase the time for light to stay in the optical absorbing layer, such that the optoelectronic flow of the elements can be increased to enhance the efficiency of the solar cell. Further, Taiwan Patent Publication No. 201007815, entitled “METAL THIN FILM USED IN OPTOELECTRONIC ELEMENT AND MANUFACTURING METHOD THEREOF” utilizes a wave array to induce surface plasma resonance to enhance the transmittance of the metal thin films. The aforementioned arts utilize surface plasma resonance techniques to enhance the efficiency of the optoelectronic elements. However, surface plasma resonance techniques must be performed with the existence of both the metal layer and non-conductive dielectric layer, and a metal grating thin layer and a dielectric layer are required, which increases the complexity and time consumption of the manufacturing process. Therefore, based on the drawbacks of the known arts, there is a need to provide a new method to enhance the efficiency of the optoelectronic element without increase the complexity of the manufacturing process.